Pipe to soil potentials have served to date as primary criteria for cathodic protection adequacy on buried or submerged pipelines. This approach has been largely successful. However, it has been demonstrated that anodic areas can exist on an apparently cathodically protected system. It is also known that potentials more positive than the commonly accepted values for full corrosion protection do not necessarily indicate active corrosion. To discover these areas using present methods of manual, closely spaced measurements is time consuming and impractical. These facts point to the desireability of providing more advanced or sophisticated techniques for monitoring the entire surface of a buried pipeline for corrosion currents. Specifically, the requirement calls for a system capable of detecting small anodic areas of low current discharge any place on the buried pipe surface without having to uncover the pipe and preferably while cathodic protection currents are still being maintained.
